phosphor-fan: Create timer class
This class can be used to call an arbitrary function
after a certain amount of time, which is set in
microseconds.
Change-Id: Ifd65bbf0c3482db4e37efc3b1ccc868e62fa0afa
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/timer.hpp b/timer.hpp
new file mode 100644
index 0000000..ea28176
--- /dev/null
+++ b/timer.hpp
@@ -0,0 +1,178 @@
+#pragma once
+
+#include <chrono>
+#include <functional>
+#include <memory>
+#include <systemd/sd-event.h>
+
+namespace phosphor
+{
+namespace fan
+{
+namespace util
+{
+
+struct EventSourceDeleter
+{
+ void operator()(sd_event_source* eventSource) const
+ {
+ sd_event_source_unref(eventSource);
+ }
+};
+
+using EventSourcePtr = std::unique_ptr<sd_event_source, EventSourceDeleter>;
+
+using EventPtr = std::shared_ptr<sd_event>;
+
+/**
+ * @class Timer
+ *
+ * This class implements a simple timer that runs an arbitrary
+ * function on expiration. The timeout value is set in microseconds.
+ * It can be stopped while it is running, and queried to see if it is
+ * running.
+ *
+ * If started with the 'repeating' argument, it will keep calling the
+ * callback function every <timeout> microseconds. If started with the
+ * 'oneshot' argument, it will just call the callback function one time.
+ *
+ * It needs an sd_event loop to function.
+ */
+class Timer
+{
+ public:
+
+ enum class TimerType
+ {
+ oneshot,
+ repeating
+ };
+
+ Timer() = delete;
+ Timer(const Timer&) = delete;
+ Timer& operator=(const Timer&) = delete;
+ Timer(Timer&&) = default;
+ Timer& operator=(Timer&&) = default;
+
+ /**
+ * @brief Constructs timer object
+ *
+ * @param[in] events - sd_event pointer, previously created
+ * @param[in] callbackFunc - The function to call on timer expiration
+ */
+ Timer(EventPtr& events,
+ std::function<void()> callbackFunc);
+
+ /**
+ * @brief Destructor
+ */
+ ~Timer();
+
+ /**
+ * @brief Starts the timer
+ *
+ * The input is an offset from the current steady clock.
+ *
+ * @param[in] usec - the timeout value in microseconds
+ * @param[in] type - either a oneshot, or repeating
+ */
+ void start(std::chrono::microseconds usec,
+ TimerType type = TimerType::oneshot);
+
+ /**
+ * @brief Stop the timer
+ */
+ void stop();
+
+ /**
+ * @brief Returns true if the timer is running
+ */
+ bool running();
+
+ /**
+ * @brief Returns the timeout value
+ *
+ * @return - the last value sent in via start().
+ *
+ * Could be used to restart the timer with the same
+ * timeout. i.e. start(getTimeout());
+ */
+ inline auto getTimeout() const
+ {
+ return timeout;
+ }
+
+ /**
+ * @brief Returns the timer type
+ */
+ inline auto getType() const
+ {
+ return type;
+ }
+
+ private:
+
+ /**
+ * @brief Callback function when timer goes off
+ *
+ * Calls the callback function passed in by the user.
+ *
+ * @param[in] eventSource - Source of the event
+ * @param[in] usec - time in micro seconds
+ * @param[in] userData - User data pointer
+ */
+ static int timeoutHandler(sd_event_source* eventSource,
+ uint64_t usec, void* userData);
+
+ /**
+ * @brief Gets the current time from the steady clock
+ */
+ std::chrono::microseconds getTime();
+
+ /**
+ * @brief Wrapper around sd_event_source_set_enabled
+ *
+ * @param[in] action - either SD_EVENT_OFF, SD_EVENT_ON,
+ * or SD_EVENT_ONESHOT
+ */
+ void setTimer(int action);
+
+
+ /**
+ * @brief Sets the expiration time for the timer
+ *
+ * Sets it to timeout microseconds in the future
+ */
+ void setTimeout();
+
+ /**
+ * @brief The sd_event structure
+ */
+ EventPtr timeEvent;
+
+ /**
+ * @brief Source of events
+ */
+ EventSourcePtr eventSource;
+
+ /**
+ * @brief Either 'repeating' or 'oneshot'
+ */
+ TimerType type = TimerType::oneshot;
+
+ /**
+ * @brief The function to call when the timer expires
+ */
+ std::function<void()> callback;
+
+ /**
+ * @brief What the timer was set to run for
+ *
+ * Not cleared on timer expiration
+ */
+ std::chrono::microseconds timeout;
+};
+
+}
+}
+}